var fs = require('fs')
var os = require('os')
var path = require('path')
var crypto = require('crypto')
var mkdirp = require('mkdirp')

function getFilename(req, file, cb) {
    crypto.pseudoRandomBytes(16, function (err, raw) {
        cb(err, err ? undefined : raw.toString('hex'))
    })
}

function getDestination(req, file, cb) {
    cb(null, os.tmpdir())
}

function DiskStorage(opts) {
    this.getFilename = (opts.filename || getFilename)

    if (typeof opts.destination === 'string') {
        mkdirp.sync(opts.destination)
        this.getDestination = function ($0, $1, cb) {
            cb(null, opts.destination)
        }
    } else {
        this.getDestination = (opts.destination || getDestination)
    }
}

DiskStorage.prototype._handleFile = function _handleFile(req, file, cb) {
    var that = this

    var hash = crypto.createHash('md5');
    that.getDestination(req, file, function (err, destination) {
        if (err) return cb(err)

        that.getFilename(req, file, function (err, filename) {
            if (err) return cb(err)

            let bufs = [];
            file.stream.on('data', function (chunk) {
                hash.update(chunk);
                bufs.push(chunk);
            });
            file.stream.on('end', function () {
                let allBuffer = Buffer.concat(bufs);
                let md5 = hash.digest('hex');
                let ext = file.originalname.split('.')[1];

                var finalPath = path.join(destination, md5);
                if (ext) {
                    finalPath = finalPath + '.' + ext;
                }
                var outStream = fs.createWriteStream(finalPath);
                outStream.on('finish', function () {
                    cb(null, {
                        destination: destination,
                        filename: filename,
                        path: finalPath,
                        size: outStream.bytesWritten,
                        hash: md5,
                        ext: ext
                    })
                });
                outStream.on('error', cb)
                outStream.write(allBuffer);
                outStream.end();
            });

        })
    })
}

DiskStorage.prototype._removeFile = function _removeFile(req, file, cb) {
    var path = file.path

    delete file.destination
    delete file.filename
    delete file.path

    fs.unlink(path, cb)
}

module.exports = function (opts) {
    return new DiskStorage(opts)
}
